HbS beta-thalassemia with a low amount of normal haemoglobin is called

• A. HbS beta plus thalassemia
• B. HbS beta zero thalassemia
• C. HbS beta-thalassemia
• D. HbC disease

Answer: (A)

The key idea is how the sickle cell HbS gene combines with a beta-thalassemia mutation. In beta-thalassemia, production of beta-globin can be reduced (beta-plus) or absent (beta-zero). When HbS is paired with a beta-thalassemia mutation that still allows some normal beta-globin to be made, you get HbS beta-plus thalassemia, in which a small amount of normal haemoglobin (HbA) remains present. If no normal beta-globin is produced, it would be HbS beta-zero thalassemia, with little or no HbA. Since the description specifies a low amount of normal haemoglobin, the correct label is HbS beta-plus thalassemia. HbC disease involves a different variant of hemoglobin and is not the correct pairing here.